Sulfide weathering in the Werenskioldbreen, Spitsbergen - A polar terrestrial analogue for gypsum deposition in the North Polar Region of Mars

Details Sulfide weathering in the Werenskioldbreen, Spitsbergen - A polar terrestrial analogue for gypsum deposition in the North Polar Region of Mars Sulfide weathering in the Werenskioldbreen, Spitsbergen - A polar terrestrial analogue for gypsum deposition in the North Polar Region of Mars

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p13b1382s&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #P13B-1382

Mathematics

Logic

[1030] Geochemistry / Geochemical Cycles, [5415] Planetary Sciences: Solid Surface Planets / Erosion And Weathering

Scientific paper

Hydrated sulfates such as gypsum are important constituents of the low-elevation areas around the North Polar residual ice cap on Mars, but the origin of hydrological process which led to the formation and accumulation of gypsum is poorly understood. To address this uncertainty, we investigated the origin of proglacial gypsum in the Werenskioldbreen, a polythermal glacier of Spitsbergen in the Svalbard archipelago east of Greenland. We measured S isotopes, major chemistry and surface water flow rates to calculate SO4 fluxes from sulfide weathering in this polar climate. Sulfides comprised 0.02 to 0.42 weight % of the fine-grained fraction of proglacial sediments and their δ34S varied over the range of +9 to +16 ‰. The δ34S of dissolved SO4 in glacier melt waters (+9 to +17 ‰) was consistent with SO4 generation being dominated by sulfide oxidation. In summer 2008, the calculated SO4 flux was ~6,200 kg/day in the main glacier stream of the Werenskioldbreen discharging to the Greenland Sea and it translated to 4.3 x 105 mol/yr-km2 based on the scale of the entire Werenskioldbreen catchment (~27.4 km2). Our measured polar SO4 flux was 6 times larger than reported estimates for pyrite-derived SO4 loading in a considerably larger (1.78 x 106 km2) watershed of Northern Canada. This implies that small glacier catchments can generate an important global-scale flux of sulfide-derived SO4. Both evaporation and freezing of glacial waters lead to precipitation, accumulation, and temporary storage of gypsum in the proglacial zone. Poor preservation of gypsum on the surface of proglacial sediments mainly results from its quick dissolution during warmer condition when the hydrological cycle is most active. The observed distribution of gypsum and hydrated sulfates around the north polar ice residual deposits of Planum Boreum on Mars matches the spatial and geochemical patterns of gypsum formation controlled by sulfide weathering in terrestrial polar environments like Werenskioldbreen. The highest occurrences of gypsum are in the eastern part of Olympia Undae Dune Field, nearby plausible fluvio-glacial features and the impact crater which might have activated confined water circulation in the past. Given that ancient aeolian strata underlying Planum Boreum are of basaltic composition and sulfides are common minor minerals in basalt, it is likely that slow weathering of this material in the presence of water ice may have contributed elevated SO4 fluxes during short-lived melting events in the past. The westward gypsum decrease in the Olympia Undae suggests re-distribution of weathering products like gypsum from the confined source area during subsequent aeolian transport. In contrast to Earth, limited water activity and prevailing dry conditions on the surface of Mars are the likely factors that account for the larger accumulation and preservation of polar gypsum on the surface and its broad aeolian distribution in the north polar depression.

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